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Home My WebLink AboutPACIFIC COAST SUPPLY WAREHOUSE - FDP200019 - SUBMITTAL DOCUMENTS - ROUND 3 - DRAINAGE REPORTFINAL DRAINAGE AND EROSION CONTROL REPORT FOR PACIFIC COAST SUPPLY A TRACT OF LAND LOCATED IN THE SOUTHWEST QUARTER OF SECTION 3, TOWNSHIP 7 NORTH, RANGE 68 WEST OF THE 6TH P.M., CITY OF FORT COLLINS, COUNTY OF LARIMER, STATE OF COLORADO ZP#: Z19-050 September 2, 2020 Rev. January 28, 2021 Rev. March 10, 2021 FINAL DRAINAGE AND EROSION CONTROL REPORT FOR PACIFIC COAST SUPPLY A TRACT OF LAND LOCATED IN THE SOUTHWEST QUARTER OF SECTION 3, TOWNSHIP 7 NORTH, RANGE 68 WEST OF THE 6TH P.M., CITY OF FORT COLLINS, COUNTY OF LARIMER, STATE OF COLORADO ZP#: Z19-050 September 2, 2020 Rev. January 28, 2021 Rev. March 10, 2021 Prepared for: Pacific Coast 12860 W. Cedar Dr. Lakewood, CO 80228 Contact: Stuart Nielson 303-659-2313 Prepared by: ZP Architects Engineers, Inc. 2727 Bryant Street, Suite 610 Denver, CO 80211 (303) 455-3322 William J. Logan, P.E. Project Engineer i Engineers Certification Statement “I hereby attest that this report for the final drainage design for the Pacific Coast Supply was prepared by me or under my direct supervision, in accordance with the provisions of the Fort Collins Stormwater Criteria Manual. I understand that the City of Fort Collins does not and will not assume liability for drainage facilities designed by others.” Registered Professional Engineer Date State of Colorado No.31705 ii TABLE OF CONTENTS PHASE II DRAINAGE REPORT I. GENERAL LOCATION AND DESCRIPTION A. Location ................................................................................................................. 1 B. Description of Property .......................................................................................... 2 II. DRAINAGE BASINS AND SUB-BASINS A. Major Basin Description ......................................................................................... 2 B. Sub-Basin Description ........................................................................................... 2 III. DRAINAGE DESIGN CRITERIA A. Regulations............................................................................................................ 3 B. Development Criteria Reference and Constraints ................................................. 3 C. Hydrological Criteria .............................................................................................. 3 D. Hydraulic Criteria ................................................................................................... 3 E. Waivers from the Criteria ....................................................................................... 4 F. Low Impact Development Four Step Process ........................................................ 4 IV. DRAINAGE FACILITY DESIGN A. General Concept ................................................................................................... 5 B. Specific Details ...................................................................................................... 7 V. CONCLUSIONS A. Compliance with Standards ................................................................................... 7 B. Drainage Concept .................................................................................................. 7 VI. LIST OF REFERENCES ............................................................................................ 8 APPENDIX A ................................................................................................................... 9 Hydrologic & Hydraulic Computations APPENDIX B ................................................................................................................. 31 Charts and Tables APPENDIX C ................................................................................................................ 40 State SW Compliance, CDOT Permit, FIRM Map, Drainage Plans iii I. GENERAL LOCATION AND DESCRIPTION A. Location The proposed Pacific Coast Supply building is located in a Tract of land located in the Southwest Quarter of Section 3, Township 7 North, Range 68 West of the 6th Principal Meridian, City of Fort Collins, County of Larimer, State of Colorado. The site is specifically located at 1012 NE I-25 Frontage Road. Vicinity Map A new structure is to be located north of the existing Pacific Coast Supply buildings. Site access is off Northeast I-25 Frontage Road to the west. To the north and east is cultivated land with further development beyond the boundary of the proposed site. To the south, the property is separated from the cultivated property by an existing 30-feet public access right-of-way. A private irrigation ditch lies along the easterly boundary. The Larimer and Weld Canal also lies to the north and east of the property, (Reference 4). A number of easements exist within the proposed property improvements. The easements consist of a 20’ water line easement, and two 15’ and 10’ easements per the plat from the K-2 Industrial Park; no description of the last two is given. The existing 10’ easement shall be removed from the property. 1 B. Description of Property The site consists of two tracts for an approximate area of 4.263 acres. The existing southern tract is currently developed, and includes the three buildings used by Pacific Coast Supply. The recently obtained north tract is undeveloped and will contain most of the new improvements. The plan is to construct a new 20,000 square-foot metal building with approximately 45,000 square-feet of hard surfaces on both tracts. The proposed development will provide additional storage space for the Pacific Coast Supply operations. The existing topography of the site slopes over a combination of native and gravel yards from the east to the west at an average slope of 1.2%. New detention and access easements for detention, maintenance and fire access are proposed. The web soil survey describes the site soils primarily as Longmont Clay and Nunn Clay Loam to Satanta Loam with a Hydrologic Soil Group C and D. Group C/D soils have a slow infiltration rate when thoroughly wet, and consist chiefly of layers that impedes the downward movement of water or soils of moderately fine to fine texture (Reference appendix B for Soil Survey Map Information). The site also has a high water table per the Geotechnical Evaluation Report by American Geoservices (Reference 6). The Larimer and Weld Canal to the east and north flows easterly under I-25 to the west. An irrigation ditch lies along the easterly most boundary and will not be affected by the proposed improvements. II. DRAINAGE BASINS AND SUB-BASINS A. Major Basin Description The site is located within the Cooper Slough/Box Elder Basin Master Drainage Study (Reference 3). This site is located within a 100-year floodplain as defined by the Federal Emergency Management Agency Community Panel numbers 08069C1001F, (Reference 4) and 08069C0982F, (Reference 5), both dated December 19, 2006. B. Sub-Basin Description Both tracts currently surface drain to the west into the ditch along NE I-25 Frontage Road. Runoff into the ditch drains south and crosses under I-25 through an existing culvert leading to the west. Offsite runoff to the site is limited from the east basins labeled OS1 and OS2. 2 The proposed site improvements will collect and surface drain the majority of the site to a water quality Bioretention pond in the middle of the site. Stormwater, along with most of the site’s proposed improvements will be directed to the detention pond located at the northwest corner of the property. The runoff collected in the pond will be directed to the west into the frontage ditch. An existing sump condition exists along the frontage ditch near the northwest corner of the property. The low spot has been identified and corrected in the proposed plans. In order to correct the low spot, some minor over lot grading is needed at the northern neighbor’s southwest corner. III. DRAINAGE DESIGN CRITERIA A. Regulations The primary criteria for this development is the “Fort Collins Stormwater Criteria Manual”, (Reference 1 and hereafter called Criteria), and the Urban Drainage Flood Control District’s Urban Storm Drainage Criteria Manuals (Reference 2 and hereafter called Manual). B. Development Criteria References and Constraints The subject area is identified within the Cooper Slough/Box Elder Basin Master Drainage Study. (Reference 3 and hereafter called Master). In addition to the Criteria, additional physical site constraints are realized due to this property being partially developed with three buildings already on site. C. Hydrological Criteria The design rainfall for the runoff generated on-site was based on the Rational Method for the 2 and 100-year rainfall events for developed conditions as established in the Criteria and Manual. The runoff results are summarized on the Drainage Plan and in Appendix A. Rainfall intensities were determined from the Criteria by using the 1-hour point rainfall values of 0.82 in/hr. for the 2-year storm event and 2.86 in/hr. for the 100-year storm event. The detention and discharge limit are based on the Criteria’s 2-year historic runoff, with the allowance that the existing impervious areas are limited to the 100-year recurrence. D. Hydraulic Criteria The capacity of the detention facility is based on the FAA method outlined in the Criteria. Both the proposed Bioretention pond (Rain Garden) and Extended 3 Drainage Basin water quality volumes are per the Criteria. E. Waivers from the Criteria The site contains unique conditions that make development per the Criteria with LID features extremely difficult. Within the proposed site, two existing buildings with floor elevations surveyed at 4973.00 feet establish an upper limit to design. At the other end, the need to eliminate the existing sump condition and still drain to the ditch establishes the lower design elevation at 4968.40 feet. The combination of full detention, an Extended Detention Basin, a Bioretention pond, Forebay, an emergency overflow depth, and a free board forces the drainage facility within a vertical design limit of 4.6 feet. This is further reduced to about 4.0 feet once a connection to the ditch is made. Due to the existing site limitations, two (2) variances are requested from the Criteria and Manual. 1. Ground cover over drainage box culvert: Variance: Due to insufficient ground cover across the drive lane, a structural concrete box culvert is proposed to accommodate drainage between the Bioretention to the detention pond. The culvert is reinforced to support an HS20 truck per ASSHTO standards. 2. Bioretention Details D-53 and D-53A: Variance: Details D-53 and D-53A depicts a 30” deep Bioretention pond filtration structure. Due to vertical site limitations and the need to control flooding, these details cannot be fully achieved. Therefor a Bioretention pond (Raingarden) with a 20” growing and drainage media similar to the Criteria is proposed. F. Low Impact Development Four Step Process The overall stormwater management strategy for the proposed project utilizes the Four Step Process to minimize adverse impacts of urbanization on receiving waters. The following is a description of how the proposed development has incorporated each step: Step 1 – Runoff Reduction Practices Bioretention and Extended Detention Basin Water Quality Systems are employed to reduce peak runoff, volume, and pollutants as part of a Low Impact Development (LID) strategy. Step 2 – Implement BMPs that Provide a Water Quality Capture Volume (WQCV) with Slow Release 4 The features identified in Step 1 will facilitate the reduction of runoff. The majority of the stormwater runoff from the proposed improvements will be intercepted through the LID features prior to exiting the site. Step 3 – Stabilized Drainageways No drainageways lie within the subject property; however, the prosed LID features will reduce sediment and potential erosion to the drainage ditch and downstream drainageway systems. Step 4 – Implement Site Specific and Other Source Control BMPs The proposed BMPs will intercept most of the north proposed improvements and approximately half the existing historic site conditions. These improvements will treat the tributary surface runoff through a forebay, followed by a Bioretention pond. Runoff from the Bioretention pond will then drain to the detention facility and further be treated by the Extended Detention Basin before exiting the site. IV. DRAINAGE FACILITY DESIGN A. General Concept Currently the surface drains primarily over native vegetation and existing gravel from east to west into the frontage drainage ditch. The proposed improvements will maintain the same drainage patterns by collecting the majority of the runoff into the detention pond along the frontage road. The ultimate outfall is to the CDOT drainage ditch. CDOT has accepted the discharge to the ditch and has issued a permit to procced. The CDOT “Notice to Proceed” permit is included in Appendix C. Minor offsite runoff will contribute to the detention pond from basin OS1. Appendix B contains the tables and charts from the Criteria and the Manual. Rainfall is based on the rational method and the City’s rainfall intensities with the site grading divided into seven onsite drainage basins. Basins A through C and OS1 define the areas directly tributary to the detention pond. Basins of direct runoff are designated DRS, DRE, DRN, DRW and OS2 are limited to the perimeter areas about the site. Basin A: Basin A comprises of the center of the property and the east storage yard area. Water collected along with basin OS1 will drain first to the Bioretention pond before transferring to the detention pond. Basin B: Basin B consists of the north roof of the building. Water off the north roof is collected in underground PVC drain lines and discharged in the detention near the northeast corner of the building. The PVC lines consist of 8” SD35 pipe and will run under 1.8 feet of head. 5 Basin C: Basin C contains the detention pond area. Water collected in basin C is combined with basins A, B and OS1 for design point DET, the emergency overflow weir. Basin DRS: The area of Direct Runoff South (DRS) represents the existing surfaces on the south side of the property. This existing runoff does not changed due to the proposed improvements. Basin DRE: Direct Runoff East (DRE) represents the small area of runoff intercepted by the existing irrigation ditch. The proposed improvements do not change the ditch or the surrounding banks along the easterly property line. Basin DRN: The area of Direct Runoff North (DRN) represents the surface behind the building. The surface runoff to the north is over native vegetation and is insignificant. Basin DRW: The area of Direct Runoff West (DRW) represents the surface tributary to the frontage road. This is the result of the berm created for the detention pond and the existing landscaped area south of the access drive lane. The drainage design consists of the main detention pond plus a LID water quality feature. The LID water quality consists of a Bioretention pond located in the middle of basin A. Water collected in the Bioretention is first channeled through a concrete lined forebay. The required forebay volume is 0.001ac-ft (44cu.ft.). The available volume is 0.004ac-ft (176cu.ft.) with a maximum 6 inch depth, reference EDB calculation sheet. The forebay will discharge its contents to the Bioretention through a 4-inch wide weir located at the middle of the forebay to the pond. In the event the weir becomes blocked, an emergency overflow point is set at the northwest corner of the forebay, directing runoff through a trickle channel and into the main pond. The Bioretention pond will consist of a 12-inch sand media over an 8-inch layer of reservoir aggregate separated by a permeable geotextile sheet. Due to a high water table, a 40 mil geomembrane liner will separate the Boirtention water from the subgrade. The Bioretention volume is 1775 cu.ft. (required 1606 cu.ft.) and is discharged through a network of underdrain pipes to a 7’x10’ drainage box situated at the northwest corner of the Bioretention pond. The open top of the 7’x10’ drainage box is designed to provide for the 100-year overflow from the Bioretention into a structural box culvert that leads to the detention pond. Seventy-five percent (75%) of the new hard surfaces is channeled through the Bioretention pond per section 6.0 of the Criteria, reference Coefficient calculation sheet. 6 A detention pond, located at the northwest corner, provides a 100-year storm volume with an Extended Detention Basin (EDB). The design EDB volume is the difference between the required EDB and the provided upstream Bioretention volume (3083cf.ft – 1775cu.ft = 1308cu.ft.) In addition to the EDB volume is the 100-year storm volume of 12,240 cu.ft for a total detention volume of 13,548cu.ft. The detention ponds outlet box uses a water quality plate to restrict the EDB runoff to a maximum 40-hour discharge limit. The 100-year volume is then controlled by a restrictor plate over the 15” outlet pipe from the drainage box. Storm release rates are based on the Criteria’s limits. The 100-year storm discharge (6.70cfs) from the pond and areas of direct runoff (5.08cfs) is limited to a combined discharge of 11.78cfs. This limit is derived from the 2-year historic pervious areas of 1.19 cfs and the historic impervious areas of 10.60 cfs. In the event the outlet box is blocked by debris, an emergency overflow weir is set at the 100-year water elevation of 4971.50 feet. This weir is designed to discharge the 100-year runoff (20.48cfs) to the ditch along the frontage road, the ultimate outfall from the site. B. Specific Details Access and maintenance to the outlet structures and to the detention features is obtained from an access and drainage easement located off the frontage road. The area of access and detention is contained in the designated easement. V. CONCLUSIONS A. Compliance with Standards The runoff calculations are based on the Criteria and Manual for the 100-year storm recurrences. In addition, water quality volumes are provided in the form of a Bioretention pond and an Extended Detention Basin per the Criteria. The storm detention volumes are based on the Modified FAA method for the 100-year storm event. The emergency overflow to the right-of-way is sized for the 100-year storm event. The outfall to the drainage ditch has been approved by CDOT. B. Drainage Concept The drainage system has been designed to convey the developed runoff to the designated detention pond in a safe and effective manner. In addition, all on site flows as well as the detention pond and its components have been sized to transfer stormwater to the drainage ditch. The proposed release rates from the detention pond will reduce the peak runoff to the 2-year historic Criteria limit. In its current condition, runoff from the site runs un-detained. The improvements being made will detain a large amount of stormwater and reduce runoff from the site so that the 100-year storm event can be conveyed safely downstream. As a result, no negative impacts are anticipated to any downstream stormwater facilities. 7 VI. REFERENCES 1. “Fort Collins Stormwater Criteria Manual”, dated revised November 2018. 2. "Urban Storm Drainage Criteria Manual", by Urban Drainage and Flood Control District, Vol. 1 and 2 dated January 2016, and Vol. 3 dated November 2010. 3. “Cooper Slough/Box Elder Basin Master Drainage Study” 4. Federal Emergency Management Agency Community Panel Number 08069C1001F, dated December 19, 2006. 5. Federal Emergency Management Agency Community Panel Number 08069C0982F, dated December 19, 2006. 6. Geotechnical Evaluation Report, Project No. 0281-D20, by American Geoservices, dated June 30, 2020 8 APPENDIX A Hydrologic & Hydraulic Computations 9 Fort Collins Stormwater Rational MethodProject Name:Pacific Coast Supply Historic RunoffCoefficentImperviousBasin Surface Types C(%)Hard SurfacesAsphalt, Conc 0.95100Rooftops 0.9590Recycled Asphalt 0.8080Gravel or Pavers 0.5040Landscape (Lawns)Playgrounds25Lawns, Sandy Soil, Flat Slope < 2% 0.102Lawns, Sandy Soil, Avg Slope 2-7% 0.152Lawns, Sandy Soil, Steep Slope > 7% 0.202Lawns, Clayey Soil, Flat Slope < 2% 0.202Lawns, Clayey Soil, Avg Slope 2-7% 0.252Lawns, Clayey Soil, Steep Slope >7% 0.352Dominant Predevelopement NRCS Soils Group: C/DAsphaltRecycled Gravel orLawns, SandyLawns, Clayey AreaAreaTotal & Conc. Rooftops Asphalt Pavers Playgrnds Flat Average Steep Flat Average Steep AverageAverage TotalArea Area Areas Areas Area Area Area Area Area Area Area Area Area Coeff. 1.00 1.00 1.00 1.10 1.20 1.25 Impervs AreaBasin Description (sq.ft.) (sq.ft.) (sq.ft.) (sq.ft.) (sq.ft.) (sq.ft.) (sq.ft.) (sq.ft.) (sq.ft.) (sq.ft.) (sq.ft.) (sq.ft.) (C)C2C5C10C25C50C100(%) (acre) BasinH1Historic Site (Pervious Area)96685 0 0 0 0 0 0 0 0 0 103547 0 0.27 0.27 0.27 0.27 0.29 0.32 0.33 2.1 2.220 H1H2Historic Site (Impervious Area)88990 4192 6550 0 78248 0 0 0 0 0 0 0 0.55 0.55 0.55 0.55 0.61 0.67 0.69 46.5 2.043 H2Runoff CoefficientsFrequency Adjustment Factor Cf10 TIME OF CONCENTRATIONProject Name:Pacific Coast Supply Historic RunoffCalculated By:WJLDATE:1/15/2021SUB-BASIN INITIAL/OVERLANDINITIALFINAL REMARKSDATATIME (ti)TIMEtcTOTALtc;ti+ttDESIGN C*Cf = AREALENGTHSLOPEtiLENGTHSLOPECHANNELVEL.ttti+ttLENGTHtc=(L/180)+10minimumC5(Ac) (ft) (ft/ft) (min) (ft) (ft/ft)CONSTANT(fps) (min) (min) (ft) (min) (min)(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (12) (13) (14)H1 0.27 2.22 300 0.018 103 200 0.008 10 0.89 4 107 500 12.8 12.8H2 0.55 2.04 114 0.003 7979 114 10.6 10.6ti=1.87(1.1-CxCf)(L^0.5)/S^1/3tt=L/(60V)tc CHECK(URBANIZED BASINS)TRAVEL TIME(tt)11 STANDARD FORM SF-3Calculated By: WJLJOB NO:Z19-050DATE:STORM DRAINAGE SYSTEM DESIGNPROJECT :NameCHECKED BY:______________ (RATIONAL METHOD PROCEDURE)DESIGN STORM:2 YearAREA DESIGNAREA (AC)RUNOFF COEFFtc (MIN)C*A (AC)I (IN/HR)Q (CFS)tc (MIN)SUM(C*A) (AC)I (IN/HR)Q (CFS)SLOPE (%)STREET FLOW(CFS)DESIGN FLOW (CFS)SLOPE (%)PIPE SIZE (IN)LENGTH (FT)VELOCITY (FPS)tt (MIN)(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22)1H1 H1 H12.22 0.27 12.8 0.59 1.99 1.192H2 H2 H22.04 0.55 10.6 1.13 2.16 2.4434Total 2-year Historic Runoff = 3.63567891011121314TRAVEL TIMEREMARKS1/15/2021STREETDESIGN POINTDIRECT RUNOFFTOTAL RUNOFF STREET PIPE 12 STANDARD FORM SF-3Calculated By: WJLJOB NO:Z19-050DATE:STORM DRAINAGE SYSTEM DESIGNPROJECT :NameCHECKED BY:______________ (RATIONAL METHOD PROCEDURE)DESIGN STORM:100 YearAREA DESIGNAREA (AC)RUNOFF COEFFtc (MIN)C*A (AC)I (IN/HR)Q (CFS)tc (MIN)SUM(C*A) (AC)I (IN/HR)Q (CFS)SLOPE (%)STREET FLOW(CFS)DESIGN FLOW (CFS)SLOPE (%)PIPE SIZE (IN)LENGTH (FT)VELOCITY (FPS)tt (MIN)(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22)1H1 H1 H12.22 0.33 12.8 0.74 6.96 5.12H2 H2 H22.04 0.69 10.6 1.41 7.52 10.6034Total 100-year Historic Runoff 1.19cfs + 10.60cfs = 11.785678910111213121/15/2021STREET PIPE TRAVEL TIMEREMARKSSTREETDESIGN POINTDIRECT RUNOFFTOTAL RUNOFF13 Fort Collins Stormwater Rational MethodProject Name:Pacific Coast SupplyCoefficient ImperviousBasin Surface Types C(%)Hard SurfacesAsphalt, Conc 0.95100Rooftops 0.9590Recycled Asphalt 0.8080Gravel or Pavers 0.5040Landscape (Lawns)Playgrounds25Lawns, Sandy Soil, Flat Slope < 2% 0.102Lawns, Sandy Soil, Avg Slope 2-7% 0.152Lawns, Sandy Soil, Steep Slope > 7% 0.202Lawns, Clayey Soil, Flat Slope < 2% 0.202Lawns, Clayey Soil, Avg Slope 2-7% 0.252Lawns, Clayey Soil, Steep Slope >7% 0.352Dominant Predevelopment NRCS Soils Group: C/D179566AsphaltRecycled Gravel orLawns, SandyLawns, Clayey AreaAreaTotal & Conc. Rooftops Asphalt Pavers Playgrnds Flat Average Steep Flat Average Steep AverageAverage TotalArea Area Areas Areas Area Area Area Area Area Area Area Area Area Coeff. 1.00 1.00 1.00 1.10 1.20 1.25 Impervs AreaBasin Description (sq.ft.) (sq.ft.) (sq.ft.) (sq.ft.) (sq.ft.) (sq.ft.) (sq.ft.) (sq.ft.) (sq.ft.) (sq.ft.) (sq.ft.) (sq.ft.) (C)C2C5C10C25C50C100(%) (acre) BasinA Center/Storage 94372 36517 16285 0 20377 0 0 0 0 21193 0 0 0.68 0.68 0.68 0.68 0.75 0.82 0.85 63.3 2.166 AB North Roof 10000 0 10000 0 0 0 0 0 0 0 0 0 0.95 0.95 0.95 0.95 1.00 1.00 1.00 90.0 0.230 BCWest Front Area19994 3260 0 0 0 0 0 0 0 16734 0 0 0.32 0.32 0.32 0.32 0.35 0.39 0.40 18.0 0.459CDRSDirect Runoff South33741 4402 3286 0 15647 0 0 0 0 10406 0 0 0.51 0.51 0.51 0.51 0.56 0.61 0.63 41.0 0.775 DRSDREDirect Runoff East2264 0 0 0 0 0 0 0 0 2264 0 0 0.20 0.20 0.20 0.20 0.22 0.24 0.25 2.0 0.052 DREDRNDirect Runoff North11130 0 0 0 5676 0 0 0 0 5454 0 0 0.35 0.35 0.35 0.35 0.39 0.42 0.44 21.4 0.256 DRNDRWDirect Runoff West8065 812 0 0 0 0 0 0 0 7253 0 0 0.28 0.28 0.28 0.28 0.30 0.33 0.34 11.9 0.185 DRWOS1 Offsite 1 15231 0 0 0 0 0 0 0 0 15231 0 0 0.20 0.20 0.20 0.20 0.22 0.24 0.25 2.0 0.350 OS1OS2 Offsite 2 5949 0 0 0 0 0 0 0 0 5949 0 0 0.20 0.20 0.20 0.20 0.22 0.24 0.25 2.0 0.137 OS2DetDetention+EDB179566 44991 29570.59 0 41700 0 0 0 0 63304.41 0 0 0.58 0.58 0.58 0.58 0.640.70 0.72 49.9 4.122 DetRGA+OS1 Rain Garden109603 36517 16285 0 20377 0 0 0 0 36424 0 0 0.62 0.62 0.62 0.62 0.68 0.74 0.77 54.8 2.516 RGNote: Detention+EDB consists of basins A, B, C, DRS, DRE, DRN, DRW Sec. 6.0 Low Impact Development (LID) Option 2 Impervious SurfacesAreaBasinDescriptionPavementRoofPavementRoofACenter/Storage36517 1300036517 13000BNorth Roof0 100000 0CWest Front Area3260 00 0DRSDirect Runoff South2477 00 0DREDirect Runoff East0 00 0DRNDirect Runoff North0 00 0DRWDirect Runoff West812 00 0Sub-Totals =43066 2300036517 13000Total New = 66066sq.ft. Total Captured =49517 sq.ft.Percent of New Hard Surfaces Tributary to RG = 75.0%Runoff CoefficientsFrequency Adjustment Factor CfTotal New Hard surfacesRG Capture Area14 TIME OF CONCENTRATIONProject Name:Pacific Coast SupplyCalculated By:WJLDATE:1/15/2021SUB-BASININITIAL/OVERLANDINITIALFINALREMARKSDATATIME (ti)TIMEtcTOTALtc;ti+ttDESIGN C*Cf = AREALENGTHSLOPEtiLENGTHSLOPECHANNELVEL.ttti+ttLENGTHtc=(L/180)+10minimumC5(Ac) (ft)(ft/ft) (min) (ft) (ft/ft)CONSTANT(fps) (min) (min) (ft) (min) (min)(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (12) (13) (14)A 0.68 2.17 206 0.005 65.88 160 0.009 20 1.85 1.44 67.31 366 12.03 12.03B 0.95 0.23 50 0.020 7.317.31 50 10.28 7.31C 0.32 0.46 144 0.036 52.6352.63 144 10.80 10.80DRS 0.51 0.77 198 0.005 90.4990.49 198 11.10 11.10DRE 0.20 0.05 22 0.068 19.3219.32 22 10.12 10.12DRN 0.35 0.26 35 0.086 18.7418.74 35 10.19 10.19DRW 0.28 0.19 17 0.250 10.0910.09 17 10.09 10.09OS1 0.20 0.35 183 0.011 102.59102.59 183 11.02 11.02OS2 0.20 0.14 102 0.010 79.4279.42 102 10.57 10.57Det 0.58 4.12 206 0.014 57.85 362 0.007 20 1.64 3.68 61.53 568 13.16 13.16RG 0.62 2.52 206 0.014 53.83 160 0.007 20 1.64 1.63 55.46 366 12.03 12.03ti=1.87(1.1-CxCf)(L^0.5)/S^1/3tt=L/(60V)tc CHECK(URBANIZED BASINS)TRAVEL TIME(tt)15 STANDARD FORM SF-3Calculated By: WJLJOB NO:Z19-050DATE:STORM DRAINAGE SYSTEM DESIGNPROJECT :NameCHECKED BY:______________ (RATIONAL METHOD PROCEDURE)DESIGN STORM:2 YearAREA DESIGNAREA (AC)RUNOFF COEFFtc (MIN)C*A (AC)I (IN/HR)Q (CFS)tc (MIN)SUM(C*A) (AC)I (IN/HR)Q (CFS)SLOPE (%)STREET FLOW(CFS)DESIGN FLOW (CFS)SLOPE (%)PIPE SIZE (IN)LENGTH (FT)VELOCITY (FPS)tt (MIN)(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22)1A A A2.17 0.68 12.0 1.48 2.05 3.04 11.0 1.55 2.12 3.302B B B0.23 0.95 7.3 0.22 2.48 0.543C C C0.46 0.32 10.8 0.15 2.14 0.3245DRS DRS DRS0.77 0.51 11.1 0.40 2.12 0.846DRE DRE DRE0.05 0.20 10.1 0.01 2.20 0.027DRN DRN DRN0.26 0.35 10.2 0.09 2.19 0.208DRW DRW DRW0.19 0.28 10.1 0.05 2.20 0.119OS1 OS1 OS10.35 0.20 11.0 0.07 2.12 0.1510OS2 OS2 OS20.14 0.20 10.6 0.03 2.16 0.0611Det Det Det4.12 0.5813.2 2.40 1.97 4.7212RG RG RG2.52 0.62 12.0 1.55 2.05 3.181314STREETDESIGN POINTDIRECT RUNOFFTOTAL RUNOFF STREET PIPE TRAVEL TIMEREMARKS1/15/202116 STANDARD FORM SF-3Calculated By: WJLJOB NO:Z19-050DATE:STORM DRAINAGE SYSTEM DESIGNPROJECT :NameCHECKED BY:______________ (RATIONAL METHOD PROCEDURE)DESIGN STORM:100 YearAREA DESIGNAREA (AC)RUNOFF COEFFtc (MIN)C*A (AC)I (IN/HR)Q (CFS)tc (MIN)SUM(C*A) (AC)I (IN/HR)Q (CFS)SLOPE (%)STREET FLOW(CFS)DESIGN FLOW (CFS)SLOPE (%)PIPE SIZE (IN)LENGTH (FT)VELOCITY (FPS)tt (MIN)(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22)1A A A2.17 0.85 12.0 1.85 7.14 13.2 12.0 1.93 7.14 13.82B B B0.23 1.00 7.3 0.23 8.63 1.983C C C0.46 0.40 10.8 0.18 7.47 1.3845DRS DRS DRS0.77 0.63 11.1 0.49 7.39 3.636DRE DRE DRE0.05 0.25 10.1 0.01 7.67 0.107DRN DRN DRN0.26 0.44 10.2 0.11 7.65 0.868DRW DRW DRW0.19 0.34 10.1 0.06 7.68 0.499OS1 OS1 OS10.35 0.25 11.0 0.09 7.41 0.6510OS2 OS2 OS20.14 0.25 10.6 0.03 7.54 0.2611Det Det Det4.12 0.7213.2 2.98 6.87 20.4812RG RG RG2.52 0.77 12.0 1.93 7.14 13.801312Maximum allowed discharge =11.78cfs Total Runoff from basins DRS, DRE, DRN, DRW = 5.08cfs Allowable Detention release = 6.70 cfs STREET PIPE TRAVEL TIMEREMARKSSTREETDESIGN POINTDIRECT RUNOFFTOTAL RUNOFF1/15/202117 Fort Collins Modified FAA Detention Project Name: Pacific Coast Supply Allowable Release Rate Qout: 6.70 cfs (Adjstd 2-year Historic) 100-Year Major Detention Runoff Coefficient C100:0.72 Inflow Peak Runoff Qin:20.48 Duration Results:(cu.ft.) (acre-ft) (min.) Max. Major Storage Vol: 12240 0.281 28 WQCV (EDB): 1308 0.030 Total Major Storm Vol: 13548 0.311 1 (min) Duration Interval Rainfall Rainfall Inflow Outflow Storage Storage Duration Intensity Volume Volume Volume Volume minutes inches / hr cubic feet cubic feet cubic feet acre feet (input) (output) (output) (output) (output) (output) 5 9.95 8902 2010 6892 0.1582 6 9.31 9995 2412 7583 0.1741 7 8.80 11023 2815 8208 0.1884 8 8.38 11996 3217 8779 0.2015 9 8.03 12932 3619 9313 0.2138 10 7.72 13814 4021 9793 0.2248 11 7.42 14605 4423 10182 0.2337 12 7.16 15374 4825 10549 0.2422 13 6.92 16097 5227 10870 0.2495 14 6.71 16809 5629 11180 0.2567 15 6.52 17500 6031 11469 0.2633 16 6.30 18037 6433 11604 0.2664 17 6.10 18556 6835 11720 0.2691 18 5.92 19068 7237 11830 0.2716 19 5.75 19549 7640 11909 0.2734 20 5.60 20041 8042 11999 0.2755 21 5.46 20517 8444 12073 0.2772 22 5.32 20943 8846 12097 0.2777 23 5.20 21401 9248 12153 0.2790 24 5.09 21859 9650 12209 0.2803 25 4.98 22278 10052 12226 0.2807 26 4.87 22657 10454 12203 0.2801 27 4.78 23094 10856 12237 0.2809 28 4.69 23498 11258 12240 0.2810 29 4.58 23755 11660 12094 0.2776 30 4.49 24091 12062 12028 0.2761 31 4.40 24416 12465 11952 0.2744 32 4.32 24732 12867 11865 0.2724 33 4.24 25038 13269 11769 0.2702 34 4.16 25335 13671 11664 0.2678 35 4.09 25624 14073 11551 0.2652 36 4.02 25904 14475 11429 0.2624 37 3.95 26177 14877 11300 0.2594 38 3.89 26443 15279 11164 0.2563 39 3.83 26702 15681 11021 0.2530 40 3.77 26955 16083 10872 0.2496 41 3.71 27202 16485 10716 0.25 42 3.65 27443 16887 10555 0.24 43 3.60 27678 17290 10389 0.24 44 3.54 27908 17692 10217 0.23 45 3.49 28134 18094 10040 0.23 46 3.44 28354 18496 9858 0.23 47 3.40 28570 18898 9672 0.22 48 3.35 28782 19300 9482 0.22 49 3.31 28989 19702 9287 0.21 50 3.26 29193 20104 9089 0.21 51 3.22 29393 20506 8887 0.20 52 3.18 29589 20908 8681 0.20 53 3.14 29782 21310 8472 0.19 54 3.10 29972 21712 8260 0.19 55 3.06 30159 22115 8044 0.18 56 3.03 30343 22517 7826 0.18 57 2.99 30524 22919 7605 0.17 58 2.96 30702 23321 7381 0.17 59 2.92 30878 23723 7155 0.16 60 2.89 31051 24125 6926 0.16 18 0 5000 10000 15000 20000 25000 30000 35000 40000 45000 50000 55000 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59Volume (Cubic Feet)Duration (Minutes) 100-Year Modified FAA Storm Detention 100-Vol 100-Inflow 100-Outflow 19 Sheet 1 of 2 Designer: Company: Date: Project: Location: 1. Basin Storage Volume A) Effective Imperviousness of Tributary Area, Ia Ia =54.8 % (100% if all paved and roofed areas upstream of rain garden) B) Tributary Area's Imperviousness Ratio (i = Ia/100)i = 0.548 C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.18 watershed inches (WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i) D) Contributing Watershed Area (including rain garden area)Area = 109,603 sq ft E) Water Quality Capture Volume (WQCV) Design Volume VWQCV =1,606 cu ft Vol = (WQCV / 12) * Area F) For Watersheds Outside of the Denver Region, Depth of d6 = in Average Runoff Producing Storm G) For Watersheds Outside of the Denver Region, VWQCV OTHER =cu ft Water Quality Capture Volume (WQCV) Design Volume H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER =cu ft (Only if a different WQCV Design Volume is desired) 2. Basin Geometry A) WQCV Depth (12-inch maximum)DWQCV =4.20 in B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical)Z = 0.00 ft / ft (Use "0" if rain garden has vertical walls) C) Mimimum Flat Surface Area AMin =1201 sq ft D) Actual Flat Surface Area AActual =5071 sq ft E) Area at Design Depth (Top Surface Area)ATop =5071 sq ft F) Rain Garden Total Volume VT=1,775 cu ft (VT= ((ATop + AActual) / 2) * Depth) 3. Growing Media Note: The City standard depth is 18", but 12" only can be achieved. 4. Underdrain System A) Are underdrains provided?1 B) Underdrain system orifice diameter for 12 hour drain time i) Distance From Lowest Elevation of the Storage y =ft Volume to the Center of the Orifice ii) Volume to Drain in 12 Hours Vol12 =cu ft iii) Orifice Diameter, 3/8" Minimum DO = in Design Procedure Form: Rain Garden (RG) W. Logan ZP Architects Engineers March 9, 2021 Pacific Coast Supply Fort Collins Bioretention UD-BMP (Version 3.07, March 2018) Choose One Choose One 18" Rain Garden Growing Media Other (Explain): YES NO 20 Sheet 2 of 2 Designer: Company: Date: Project: Location: 5. Impermeable Geomembrane Liner and Geotextile Separator Fabric A) Is an impermeable liner provided due to proximity of structures or groundwater contamination? 6. Inlet / Outlet Control A) Inlet Control 7. Vegetation 8. Irrigation A) Will the rain garden be irrigated? Notes: Design Procedure Form: Rain Garden (RG) W. Logan ZP Architects Engineers March 9, 2021 Pacific Coast Supply Fort Collins Bioretention Plantings do not require Irrigation, and the No selection (Section 8) clears any Geomembrane selection (Section 5) above. Choose One Choose One Choose One Sheet Flow- No Energy Dissipation Required Concentrated Flow- Energy Dissipation Provided Plantings Seed (Plan for frequent weed control) Sand Grown or Other High Infiltration Sod Choose One YES NO YES NO 21 Sheet 1 of 3 Designer: Company: Date: Project: Location: 1. Basin Storage Volume A) Effective Imperviousness of Tributary Area, Ia Ia =49.9 % B) Tributary Area's Imperviousness Ratio (i = Ia / 100 )i = 0.499 C) Contributing Watershed Area Area = 4.122 ac D) For Watersheds Outside of the Denver Region, Depth of Average d6 = in Runoff Producing Storm E) Design Concept (Select EURV when also designing for flood control)1 F) Design Volume (WQCV) Based on 40-hour Drain Time VDESIGN= ac-ft (VDESIGN = (1.0 * (0.91 * i3 - 1.19 * i2 + 0.78 * i) / 12 * Area ) G) For Watersheds Outside of the Denver Region, VDESIGN OTHER= ac-ft Water Quality Capture Volume (WQCV) Design Volume (VWQCV OTHER = (d6*(VDESIGN/0.43)) H) User Input of Water Quality Capture Volume (WQCV) Design Volume VDESIGN USER=0.0300 ac-ft (Only if a different WQCV Design Volume is desired) I) NRCS Hydrologic Soil Groups of Tributary Watershed i) Percentage of Watershed consisting of Type A Soils HSG A =% ii) Percentage of Watershed consisting of Type B Soils HSG B =% iii) Percentage of Watershed consisting of Type C/D Soils HSG C/D =% J) Excess Urban Runoff Volume (EURV) Design Volume For HSG A: EURVA = 1.68 * i1.28 EURVDESIGN = ac-f t For HSG B: EURVB = 1.36 * i1.08 For HSG C/D: EURVC/D = 1.20 * i1.08 K) User Input of Excess Urban Runoff Volume (EURV) Design Volume EURVDESIGN USER= ac-f t (Only if a different EURV Design Volume is desired) 2. Basin Shape: Length to Width Ratio L : W = 2.0 : 1 (A basin length to width ratio of at least 2:1 will improve TSS reduction.) 3. Basin Side Slopes A) Basin Maximum Side Slopes Z = 4.00 ft / ft (Horizontal distance per unit vertical, 4:1 or flatter preferred) 4. Inlet A) Describe means of providing energy dissipation at concentrated inflow locations: 0.030 5. Forebay A) Minimum Forebay Volume VFMIN =0.001000 ac-ft (VFMIN = 2% of the WQCV) B) Actual Forebay Volume VF =0.00404 ac-ft C) Forebay Depth (DF = 18 inch maximum) DF =6.0 in D) Forebay Discharge i) Undetained 100-year Peak Discharge Q100 =13.80 cfs ii) Forebay Discharge Design Flow QF =0.28 cfs (QF = 0.02 * Q100) E) Forebay Discharge Design F) Discharge Pipe Size (minimum 8-inches)Calculated DP =in G) Rectangular Notch Width Calculated WN =4.0 in Design Procedure Form: Extended Detention Basin (EDB) Pacific Coast Supply ZP Architects Engineers March 9, 2021 W. Logan UD-BMP (Version 3.07, March 2018) Riprap field Flow too small for berm w/ pipe &KRRVH2QH ([FHVV8UEDQ5XQRII9ROXPH(859 &KRRVH2QH :DOOZLWK5HFW1RWFK %HUP:LWK3LSH :DWHU4XDOLW\&DSWXUH9ROXPH:4&9 :DOOZLWK91RWFK:HLU \ 0.07076 (3083 cu.ft.) RG Volume provided = 1775 cu.ft. Required volume calculated by the program Design EDB = 3083-1775 = 1308 cu.ft. 1308/43560=0.0300 ac.ft.(1308 cu.ft.) Default volume calculated by the program Line 1.h = 0.0300ac.ft. x 2% = 0.0010 Actual forebay volume provided overrides minimum above. See calculation sheet for Volumes Provided. Weir notch from forebay to RG 22 Detention Pond Volume Calculations Incremental Area = (A1+A2+SQRT(A1*A2))*D/3 Pond Incremental Accumulated Design Design Design Stage Elev. Cont. Area Vol. Vol. Vol. Vol. Stage Vol. Elev. (ft) (ft) (ft^2) (ft^3) (ft^3) (ft^3) (ft) (ft) 0 69.08 0 0 0 0.42 69.50 1171 164 164 0.92 70.00 3570 1131 1295 EDB 1.42 70.50 6992 2593 3888 1308 0.92 70.00 WQCV 1.92 71.00 9904 4203 8091 2.42 71.50 11898 5443 13534 2.92 72.00 13811 6421 19955 13548 2.67 71.50 100-YR BioRetention (Rain Garden) Volume Calculations Pond Incremental Accumulated Design Design Design Stage Elev. Cont. Area Vol. Vol. Vol. Vol. Stage Vol. Elev. (ft) (ft) (ft^2) (ft^3) (ft^3) (ft^3) (ft) (ft) 0 71.40 5071 0 0 Bio 0.35 71.75 5071 1775 1775 1775 0.35 71.75 WQCV Forebay Volume Calculations (Forebay located at entrance to BioRetention Pond) Pond Incremental Accumulated Design Design Design Stage Elev. Cont. Area Vol. Vol. Vol. Vol. Stage Vol. Elev. (ft) (ft) (ft^2) (ft^3) (ft^3) (ft^3) (ft) (ft) 0 71.50 0 0 0 0.50 72.00 1054 176 176 176 0.50 72.00 23 Sumped Horizontal Drainage Drop Box at Bioretention (RG) Box Dimensions:Width =7 ft Depth =10 ft Overflow Weir Top Edge Ht, Ho =71.75 ft (Measured to bottom of Stage) Overflow Weir Perimeter Length , Lo =34 ft Box Horz. Free Open Area, Ao =70 ft^2 Overflow Grate Opening % =75 % (Percentage of Opening, Ao) Grate Clogging % =50 % (Percentage of Grate Opening) Weir Discharge Coefficient =3.3 Step =0.025 Orifice Discharge Coefficient =0.62 Horz. Box Horz.Max. Weir Orifice Design Stage Depth Flow Flow Flow (ft)(ft)(cfs)(cfs)(cfs) T.O. Sand 71.40 -0.35 0.0 0.0 0.0 71.43 -0.32 0.0 0.0 0.0 71.45 -0.30 0.0 0.0 0.0 71.48 -0.27 0.0 0.0 0.0 71.50 -0.25 0.0 0.0 0.0 71.53 -0.22 0.0 0.0 0.0 71.55 -0.20 0.0 0.0 0.0 71.58 -0.17 0.0 0.0 0.0 71.60 -0.15 0.0 0.0 0.0 71.63 -0.12 0.0 0.0 0.0 71.65 -0.10 0.0 0.0 0.0 71.68 -0.07 0.0 0.0 0.0 71.70 -0.05 0.0 0.0 0.0 71.73 -0.02 0.0 0.0 0.0 T.O. Box 71.75 0.00 0.0 0.0 0.0 71.78 0.03 0.4 20.7 0.4 71.80 0.05 1.3 29.2 1.3 71.83 0.08 2.3 35.8 2.3 71.85 0.10 3.5 41.3 3.5 71.88 0.13 5.0 46.2 5.0 71.90 0.15 6.5 50.6 6.5 71.93 0.18 8.2 54.6 8.2 71.95 0.20 10.0 58.4 10.0 71.98 0.23 12.0 62.0 12.0 Max. Stage 72.00 0.25 14.0 65.3 14.0 Design Point RG 72.03 0.28 16.2 68.5 16.2 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 71.4071.4371.4571.4871.5071.5371.5571.5871.6071.6371.6571.6871.7071.7371.7571.7871.8071.8371.8571.8871.9071.9371.9571.9872.0072.03Flow (cfs)Stage (ft) Bioretention Outlet Box Flow (cfs) 24 Project: Pipe ID: Design Information (input) Design Discharge Q = 6.9 cfs Box Width W = 2.50 ft Box Height H = 1.00 ft Inlet Edge Type (choose from pull-down list) Inlet Type = Square Edge w/ 90-15 Deg. Headwall Inlet Invert Elevation Ie = 69.83 ft Outlet Invert Elevation Oe = 69.58 ft Culvert Length L = 103.0 ft Manning's Roughness N-Value N = 0.013 Bend Loss Coefficient Kb =0.00 Exit Loss Coefficient Kx =0.02 Tailwater Depth Elevation El. Yt = 71.50ft Calculations (output) Box Cross Sectional Area Ao = 2.50 sq ft Culvert Slope So = 0.0024 ft/ft Normal Flow Depth Yn = 0.79 ft Critical Flow Depth Yc = 0.62 ft Headwater Depth by Inlet Control Headwater Depth by Inlet Control HW-inlet= 1.05 ft Headwater Depth by Outlet Control Tailwater Depth for Design d = 1.82 ft Friction Loss Coefficient over Culvert Length Kf =3.20 Sum of All Loss Coefficients K's =3.72 Headwater Depth by Outlet Control HW-outlet= 2.13 ft Design Headwater Depth HW= 2.13 ft HW/D Ratio =HW/D= 2.13 Headwater Depth For Box Culvert Pacific Coast Double Rectangular Culvert between RG and Detention Pond Q=RD_100-year/2 = 13.80cfs/2 = 6.9 cfs/box Inflow head should does not exceed overflow depth = 72ft - 69.83ft = 2.17ft. 25 where Cd 0.60:= Qwqcv d 1 2 4 Cd 2 g h 1 d1 2 -  d 2 2 4 Cd 2 g h2 d2 2 - +:=Qwqcv 0.0110 ft3 sec = Approximate WQCV Drain Time:Drain_Time WQCV Qwqcv 1hr 3600sec := Drain_Time 33hr=(approxiomatly) Provide 2 rows at 4" o.c. vertically in face of drainage box with (1) one 1/2-inch diameter holes per row. Trashrack Opening Area: D 1 2 in:=Aot 0.042 ft()2 4 2:=Aot 0.003ft2= At Aot 77 e 0.124-D( ):=At 0.20ft2= (29 in^2 min., 55 in^2 provided) Use stainless steel well screen #93 Vee w/ 0.139 " wire opening, # 156 VEE support rods on 3/4" o.c., screen thickness 0.31" w/ 5" wide min. opening. WQCV Release Plate: The design EDB WQCV is the difference between the Required EDB and Provided Bioreteion (RG) volumes calculated in the RG and EDB worksheets. EDBrqd 3083 ft3:= RGprvd 1775 ft3:= WQCV EDBrqd RGprvd-:=WQCV 1308ft3= Two 1/2" diameter outlets:d 1 0.0417ft= d 2 0.0417ft= ElevWQCV 70ft=DepthWQCV ElevWQCV 69.08 ft-:=DepthWQCV 0.92ft= h 1 DepthWQCV d 1 2 -:=h 1 0.899ft= h 2 DepthWQCV 4 12 ft d2 2 + -:=h 2 0.566ft= Discharge from water quality plate: 26 Detention Discharge Box with Grate Flow Rate Box Dimensions:Width =3 ft Depth =3 ft Overflow Weir Top Edge Ht, Ho =71.10 ft (Measured to bottom of Stage) Overflow Weir Perimeter Length , Lo =9 ft Box Horz. Free Open Area, Ao =9 ft^2 Overflow Grate Opening % =75 % (Percentage of Opening, Ao) Grate Clogging % =50 % (Percentage of Grate Opening) Weir Discharge Coefficient =3.3 Step =0.1 Orifice Discharge Coefficient =0.62 Depth Horz. Box Vert. Horz.Max. above Top Weir Front Weir Orifice Design Stage 70 ft Flow Flow Flow Flow (ft)(ft)(cfs)(cfs)(cfs)(cfs) Crest at Front 70.0 0.00 0.0 0.0 0.0 0.0 70.1 0.10 0.0 0.3 0.0 0.3 70.2 0.20 0.0 0.9 0.0 0.9 70.3 0.30 0.0 1.6 0.0 1.6 70.4 0.40 0.0 2.4 0.0 2.4 70.5 0.50 0.0 3.4 0.0 3.4 70.6 0.60 0.0 4.4 0.0 4.4 70.7 0.70 0.0 5.5 0.0 5.5 70.8 0.80 0.0 6.7 0.0 6.7 70.9 0.90 0.0 7.9 0.0 7.9 71.0 1.00 0.0 9.2 0.0 9.2 Top of Box 71.1 1.10 0.0 10.6 0.0 10.6 71.2 1.20 0.9 10.6 5.3 11.5 71.3 1.30 2.6 10.6 7.5 13.2 71.4 1.40 4.8 10.6 9.2 15.4 T.O. 100-Year 71.5 1.50 7.4 10.6 10.6 18.0 * 71.6 1.60 10.4 10.6 11.9 21.0 71.7 1.70 13.6 10.6 13.0 23.6 71.8 1.80 17.1 10.6 14.0 24.6 71.9 1.90 20.9 10.6 15.0 25.6 T.O. Overflow 72.0 2.00 24.9 10.6 15.9 26.5 * Top of box will not govern release rate from pond. See restrictor plate calculation for discharge rate control. 0.0 5.0 10.0 15.0 20.0 25.0 70.070.170.270.370.470.570.670.770.870.971.071.171.271.371.471.571.671.771.871.972.0Flow (cfs)Stage (ft) 100-Year Detention Box Inflow through Top of Box (cfs) 27 Project: Basin ID: X 1 #1 Vertical #2 Vertical Sizing the Restrictor Plate for Circular Vertical Orifices or Pipes (Input)Orifice Orifice Water Surface Elevation at Design Depth Elev: WS = 71.50 feet Pipe/Vertical Orifice Entrance Invert Elevation Elev: Invert = 69.00 feet Required Peak Flow through Orifice at Design Depth Q = 6.70 cfs Pipe/Vertical Orifice Diameter (inches)Dia = 15.0 inches Orifice Coefficient Co = 0.65 Full-flow Capacity (Calculated) Full-flow area Af = 1.23 sq ft Half Central Angle in Radians Theta = 3.14 rad Full-flow capacity Qf = 8.8 cfs Percent of Design Flow = 131% Calculation of Orifice Flow Condition Half Central Angle (0<Theta<3.1416)Theta = 1.95 rad Flow area Ao = 0.89 sq ft Top width of Orifice (inches)To = 13.97 inches Height from Invert of Orifice to Bottom of Plate (feet)Yo = 0.85 feet Elevation of Bottom of Plate Elev Plate Bottom Edge = 69.85 feet Resultant Peak Flow Through Orifice at Design Depth Qo = 6.7 cfs Width of Equivalent Rectangular Vertical Orifice Equivalent Width = 1.05 feet Centroid Elevation of Equivalent Rectangular Vertical Orifice Equiv. Centroid El. = 69.43 feet Pacific Coast Detention Outlet RESTRICTOR PLATE SIZING FOR CIRCULAR VERTICAL ORIFICES 28 Emergency overflow from pond: Use a retangular contracted weir: Qof Cw L 0.2 H-()Hb:= where Cw 3.33:= b 3 2 := Hw 6.00 in:=Hw 0.5ft= Detention flow through is:Qof 20.48 cfs:=Design point DET Required width of weir at 6" depth: Width root Cw L 0.2 Hw-( ) Hw b Qof-L,:= Width 17.5ft= Use an 18' wide emergency overflow wier with 6" flow depth from detention pond. 29 PVC SD35 Roof Drain Lines Pipe Top Invert = 73.25 ft Pipe Outlet Invert = 71.5 ft Numbr of Pipes 1 1 2 Pipe Size = 10.000 in 8.000 in 6.000 in Pipe I.D. = 9.900 in 7.920 in 5.915 in Area = 76.977 in^2 49.265 in^2 27.479 in^2 0.535 ft^2 0.342 ft^2 0.191 ft^2 Q100 = 1.98 cfs 1.98 cfs 0.99 cfs Flow Velocity = 3.708 fps 5.794 fps 5.194 fps HW C = 150 150 150 Pipe Length = 226 ft 226 ft 226 ft Pipe Slope = 0.008 0.008 0.008 Pipe Rise = 1.75 ft 1.75 ft 1.75 ft HW Head Loss = 0.9 ft 2.7 ft 3.1 ft Kinetic Head = 0.2 ft 0.5 ft 0.4 ft Required Total Head = 1.1 ft 3.2 ft 3.5 ft Depth Rqd BTWN Invert at inlet = -0.2 ft 1.8 ft 2.0 ft -0.055 0.445 0.497 Renolds Num. 3,016,430 3,770,538 2,524,316 OK Turbulant OK Turbulant OK Turbulant Outlet Invert = 71.50 ft 71.50 ft 71.50 ft Head Elevation = 71.28 ft 73.28 ft 73.49 ft Required head elevation is below grade elevation = 74ft. Use 8" PVC underground PVC pipes 30 APPENDIX B Charts and Tables 31 32 33 34 35 Hydrologic Soil Group—Larimer County Area, Colorado (Pacific Coast Supply) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 9/8/2020 Page 1 of 44494360449438044944004494420449444044944604494480449450044943604494380449440044944204494440449446044944804494500499900499920499940499960499980500000500020500040500060500080500100500120 499900 499920 499940 499960 499980 500000 500020 500040 500060 500080 500100 500120 40° 36' 4'' N 105° 0' 4'' W40° 36' 4'' N104° 59' 54'' W40° 35' 59'' N 105° 0' 4'' W40° 35' 59'' N 104° 59' 54'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84 0 50 100 200 300 Feet 0 15 30 60 90 Meters Map Scale: 1:1,070 if printed on A landscape (11" x 8.5") sheet. Soil Map may not be valid at this scale.36 MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Rating Polygons A A/D B B/D C C/D D Not rated or not available Soil Rating Lines A A/D B B/D C C/D D Not rated or not available Soil Rating Points A A/D B B/D C C/D D Not rated or not available Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Larimer County Area, Colorado Survey Area Data: Version 15, Jun 9, 2020 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Jul 19, 2018—Aug 10, 2018 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Hydrologic Soil Group—Larimer County Area, Colorado (Pacific Coast Supply) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 9/8/2020 Page 2 of 437 Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 53 Kim loam, 1 to 3 percent slopes B 0.0 0.1% 63 Longmont clay, 0 to 3 percent slopes D 1.3 29.3% 74 Nunn clay loam, 1 to 3 percent slopes C 2.2 51.5% 94 Satanta loam, 0 to 1 percent slopes C 0.8 19.1% Totals for Area of Interest 4.3 100.0% Description Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (A/D, B/D, and C/D). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. Hydrologic Soil Group—Larimer County Area, Colorado Pacific Coast Supply Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 9/8/2020 Page 3 of 4 38 Rating Options Aggregation Method: Dominant Condition Aggregation is the process by which a set of component attribute values is reduced to a single value that represents the map unit as a whole. A map unit is typically composed of one or more "components". A component is either some type of soil or some nonsoil entity, e.g., rock outcrop. For the attribute being aggregated, the first step of the aggregation process is to derive one attribute value for each of a map unit's components. From this set of component attributes, the next step of the aggregation process derives a single value that represents the map unit as a whole. Once a single value for each map unit is derived, a thematic map for soil map units can be rendered. Aggregation must be done because, on any soil map, map units are delineated but components are not. For each of a map unit's components, a corresponding percent composition is recorded. A percent composition of 60 indicates that the corresponding component typically makes up approximately 60% of the map unit. Percent composition is a critical factor in some, but not all, aggregation methods. The aggregation method "Dominant Condition" first groups like attribute values for the components in a map unit. For each group, percent composition is set to the sum of the percent composition of all components participating in that group. These groups now represent "conditions" rather than components. The attribute value associated with the group with the highest cumulative percent composition is returned. If more than one group shares the highest cumulative percent composition, the corresponding "tie-break" rule determines which value should be returned. The "tie-break" rule indicates whether the lower or higher group value should be returned in the case of a percent composition tie. The result returned by this aggregation method represents the dominant condition throughout the map unit only when no tie has occurred. Component Percent Cutoff: None Specified Components whose percent composition is below the cutoff value will not be considered. If no cutoff value is specified, all components in the database will be considered. The data for some contrasting soils of minor extent may not be in the database, and therefore are not considered. Tie-break Rule: Higher The tie-break rule indicates which value should be selected from a set of multiple candidate values, or which value should be selected in the event of a percent composition tie. Hydrologic Soil Group—Larimer County Area, Colorado Pacific Coast Supply Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 9/8/2020 Page 4 of 4 39 APPENDIX C State SW Compliance, CDOT Permit, FIRM Map, Drainage Plans 40 Stormwater Facility Name: Facility Location & Jurisdiction: User (Input) Watershed Characteristics User Defined User Defined User Defined User Defined Watershed Slope =0.012 ft/ft Stage [ft] Area [ft^2] Stage [ft] Discharge [cfs] Watershed Length-to-Width Ratio = 2.00 L:W 0.00 0 0.000 0.000 Watershed Area = 4.12 acres 0.42 1,171 0.420 0.005 Watershed Imperviousness = 49.9% percent 0.92 3,570 0.920 0.110 Percentage Hydrologic Soil Group A = 0.0% percent 1.42 6,992 1.42 3.38 Percentage Hydrologic Soil Group B = 0.0% percent 1.92 9,904 1.92 5.04 Percentage Hydrologic Soil Groups C/D = 100.0% percent 2.42 11,898 2.42 6.70 2.92 13,811 2.92 20.48 User Input: Detention Basin Characteristics WQCV Design Drain Time = 40.00 hours After completing and printing this worksheet to a pdf, go to: https://maperture.digitaldataservices.com/gvh/?viewer=cswdif, create a new stormwater facility, and attach the pdf of this worksheet to that record. Routed Hydrograph Results Design Storm Return Period =WQCV 2 Year 5 Year 10 Year 25 Year 50 Year 100 Year Two-Hour Rainfall Depth =0.53 0.98 1.36 1.71 2.31 2.91 3.67 in Calculated Runoff Volume =0.070 0.159 0.274 0.384 0.590 0.779 1.043 acre-ft OPTIONAL Override Runoff Volume =0.03 acre-ft Inflow Hydrograph Volume =0.030 0.158 0.274 0.383 0.590 0.779 1.043 acre-ft Time to Drain 97% of Inflow Volume =23 12 7 6 5 4 3 hours Time to Drain 99% of Inflow Volume =27 22 17 14 10 8 7 hours Maximum Ponding Depth =0.79 1.21 1.44 1.68 2.12 2.46 2.66 ft Maximum Ponded Area =0.067 0.126 0.163 0.195 0.245 0.276 0.294 acres Maximum Volume Stored =0.023 0.062 0.096 0.140 0.237 0.325 0.383 acre-ft Stormwater Detention and Infiltration Design Data Sheet Pacific Coast 1012 NE I-25 Frontage Road, Fort Collins, Colorado Workbook Protected Worksheet Protected 6573312.xlsm, Design Data 3/8/2021, 6:22 PM 41 Doing_Clear_Formatting =Yes CountA=1 0 1 2 3 #N/A #N/A 0 1 2 3 #N/A #N/A Check Data Set 1 Check Data Set 1 Stormwater Detention and Infiltration Design Data Sheet Area Discharge 0 5 10 15 20 25 0.1 1 10FLOW [cfs]TIME [hr] 100YR IN 100YR OUT 50YR IN 50YR OUT 25YR IN 25YR OUT 10YR IN 10YR OUT 5YR IN 5YR OUT 2YR IN 2YR OUT WQCV IN WQCV OUT 0 0.5 1 1.5 2 2.5 3 0.1 1 10 100PONDING DEPTH [ft]DRAIN TIME [hr] 100YR 50YR 25YR 10YR 5YR 2YR WQCV 6573312.xlsm, Design Data 3/8/2021, 6:22 PM 42 43 44 45 46 47 PACIFIC COAST SUPPLYBUILDING 3 STORAGE WAREHOUSE1012 NE FRONTAGE ROADFORT COLLINS, COLORADO 80524UTILITY PLANSA REC. NO. 20180002354 89,823 sq. ft. 2.062 ac. LOT1, K-2 INDUSTRIAL PARK P.U.D. 95,852 sq. ft. 2.200 ac.I-25 FRONTAGE ROADI-25 CNTR LINEA C DRS DRW OS2 DRN DRE OS1 B 48